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Tropical Storm Greg Discussion Number 3
NWS Central Pacific Hurricane Center Honolulu HI EP082023
500 AM HST Mon Aug 14 2023
Deep convection associated with Greg continues to develop near and
west of the low-level circulation this morning, which has become
partially exposed due to southeasterly shear estimated to be near
10 to 15 kt. An ASCAT pass from several hours ago, however,
revealed the system has a well-defined circulation, with 35 kt
winds depicted north of the center. Based on the ASCAT data and
subjective Dvorak intensity estimates ranging from T2.0 to T3.0
between PHFO, SAB, AND JTWC, the initial intensity is held at 35 kt.
The initial motion for this advisory is 270/11 kt, as Greg
continues to move south of the subtropical ridge. No significant
change in this steering is expected over the next couple of days.
Thereafter, a gradual turn to the west-southwest is forecast as the
weakening system becomes steered by low- to mid-level flow. Similar
to the previous advisory, the track guidance continues to shift
slowly southward, with Greg passing far south of the Hawaiian
Islands later this week. This forecast track reflects that and lies
near a combination of the previous forecast, HCCA, and TVCE.
Despite the tropical storm being located over very warm waters and
within a relatively moist environment, the aforementioned
southeasterly shear will continue to inhibit strengthening
initially. Guidance shows this shear persisting over the next 12 to
18 h before trending down. Therefore, the intensity is held steady
for the first 12 h, then followed by some modest strengthening
between 24 and 48 h. Beyond that, drier mid-level air along with
increasing shear and slightly cooler waters should result in a
gradual weakening trend, with Greg becoming post-tropical by day 5.
FORECAST POSITIONS AND MAX WINDS
INIT 14/1500Z 11.3N 140.9W 35 KT 40 MPH
12H 15/0000Z 11.4N 142.6W 35 KT 40 MPH
24H 15/1200Z 11.6N 144.9W 40 KT 45 MPH
36H 16/0000Z 11.8N 147.3W 45 KT 50 MPH
48H 16/1200Z 12.2N 149.7W 45 KT 50 MPH
60H 17/0000Z 12.6N 152.2W 45 KT 50 MPH
72H 17/1200Z 12.7N 154.7W 40 KT 45 MPH
96H 18/1200Z 12.3N 159.8W 35 KT 40 MPH
120H 19/1200Z 11.7N 164.9W 30 KT 35 MPH...POST-TROP/REMNT LOW
$$
Forecaster Gibbs/Birchard
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